July 2005 – May 2006
The Barrow Offshore Wind Farm (BOWF) comprises 30 wind turbines each capable of producing 3.0MW of electricity. The output for the whole site could be up to 90MW or enough electricity to power 87,000 average homes.
A single buried 132kV subsea export cable; approximately 26 km long transmits the offshore power to the shore just south of Heysham Power Station.
In April 2005 the Vestas-Kellogg Brown & Root (VKBR) Consortium awarded the installation subcontract to MPI Offshore (MPIO). The scope of works included:
- Transportation of the foundation components from the fabricators in Belgium
- Installation of the foundations in the field
- Receiving the turbine components at an onshore facility with an element of sub assembly works
- Turbine installation in the field
- Installation of the turbine interconnecting array cables and installation of the single export cable
- Load out and installation of the 480t offshore transformer structure, fully fitted out onshore
For the offshore construction period an onshore base was established in Belfast, at the Harland and Wolff Shipyard (H & W). This facility was ideally located, gave 24 hour access to berth MPI Resolution, had ample storage areas needed to stock pile foundation and turbine components and had a principle gantry crane with 800t lift capacity, ideal for load out operations. Transit times from H & W facility to the BOWF field and return were in the order of twelve hours.
The first phase of the offshore construction works involved the installation of the foundation components, the monopiles, transition pieces and j-tube assemblies. As all the monopiles were in excess of MPI Resolution’s 300t crane capacity an upending frame was purposely designed and manufactured for the job. With the monopile positioned on the seabed, in the majority of cases, they were driven to final depth, but on occasions, piles “refused” and drilling techniques had to be employed to complete the works. The foundation installation, start to finish, ran for the summer and autumn period of 2005.
Running in parallel with the foundations was installation of the export cable, ploughed to depth from a separate vessel to MPI Resolution and the installation of the offshore transformer by means of a 1500t floating crane.
Unprecedented in the industry, MPIO made plans to install the turbines through the winter period and in early December 2005 the first turbine was erected in the field. This construction phase was only possible due to MPI Resolution’s unique ability to jack clear of the sea, to form a fixed, stable platform from which the turbine construction activities could safely proceed.
Also at this phase MPIO introduced another first in the industry by installing the array cables simultaneously with the turbine build, all from the single vessel, MPI Resolution. This was brought about by deploying the only ROV (Remotely Operated Vehicle) of its type. The ROV (LBT1) was purposely developed for this operation in collaboration with subsea cable equipment specialists, SMD. Separate details of LBT1 are available on a MPIO fact sheet.
In both the foundation and turbine/array cable phases of works divers were used on a regular basis for planned and intervention dive operations. Again, due to MPI Resolution’s “jacked” status the divers, by means of an “A-frame” dive basket, could be deployed at times when traditional dive support vessels could not operate.
In early May 2006 the last turbine and array cable were installed. The turbine construction period had run through the whole winter season to complete the project works. This track record proved MPI Resolution’s capacity in such conditions, and opened to MPIO, the opportunity of continuous round the year operations.